A mass damper or damper for short, damps vibrations in a vibrating system by having as the central active element a vibrating mass of its own, which vibrates opposite the vibration of the vibrating main object of the vibrating system. The vibrating mass of the damper may also be called counter vibrating mass, because it vibrates in antiphase to the exciting vibration of the vibrating system. In many mass dampers, the counter vibrating mass or damping mass forms, together with a damping spring, a physical pendulum, whose resonant frequency or damping characteristics is set at a certain ratio to the vibration frequency of the vibrating system, which such vibration frequency is to be damped. The mass damper can perform great deflections at the damping spring resonant frequency and extract vibration energy from the vibrating structure to be damped for its own vibration motions.
The present invention is based on the general idea of using the bistable flux nature of permanent magnets to produce a bistable magnetic force on magnetic disks mediated by a spring material to manufacture a magnetic spring assembly for mass dampers. The characteristics of the bistable magnetic response in the present invention is similar to the “Dual Position Latching Solenoid,” U.S. Pat. No. 3,022,450, Pat. Date Feb. 20, 1962 and “Methods for Controlling the Path of Magnetic Flux from a Permanent Magnet and Devices Incorporating the Same,” U.S. Pat. No. 6,246,561, Pat. Date Jun. 12, 2001. The magnetic response and magnetic pole movements is best described in U.S. Pat. No. 6,246,561, but the present invention has the solenoidal shape and cylindrical magnetic flux paths as in U.S. Pat. No. 3,022,450, although having external moveable magnetic poles as in U.S. Pat. No. 6,246,561.
In the aforementioned patents and when the power is removed from the control coils, the magnetic flux from the permanent magnet in a magnet body is given dual paths in the magnet body to form dual pole faces with the amount of magnetic flux in a given direction controlled by the gap between the magnet body and the moveable magnetic poles. This characteristic of the flux is called bistable as little change in the gap can cause a large change to the amount of flux and thus the magnetic force in a given direction, as the magnetic force is a function of the gap distance squared.
In the present invention, the flux from the permanent magnet is controlled by the design of the flux path to flow in equal directions through a magnetic body about the permanent magnet. Magnetic poles of equal characteristics and free to move with respect to the magnetic body are placed on either side of the magnetic body and prevented from magnetically latching to the magnet body by a non-magnetic spring material. The magnetic poles then become part of the flux path with the spring material determining the gap between the magnet body and the magnetic poles. When the gap is the same, the amount of flux in either direction through the magnetic body and magnetic poles are the same. As such the magnetic force on the magnetic poles are the same.
By firmly connecting the magnetic poles so they move as a single unit and when an external force is applied to the magnetic pole unit to change the gap from one side of the magnet body to the other, a gap offset will result. This gap offset establishes a magnetic force offset on the magnetic pole unit opposed by a compression force offset in the spring materials. Then when the external force is remove, the spring nature of the spring material will cause the magnetic poles to vibrate like a spring, damped by the magnetic force on the magnetic poles.